Tips and tricks
Modern blanking and piercing dies
MODERN BLANKING AND PIERCING DIES
CONTENTS
- Blanking and Piercing Dies
- Sectional Punch and Die Construction
MACHINERY'S REFERENCE SERIES
The Industrial Press, New York, 1914
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Modern blanking and piercing dies
BLANKING AND PIERCING DIES
Punches and dies are made in such a variety of designs and for so many different purposes that it is difficult, if not impossible, to treat the subject of die construction and design in a general way and present fundamental principles which can be applied universally in the art of die making. For that reason, die makers in describing their methods and practice have almost invariably confined their articles to specific die designs instead of attempting to deal with the theories of the subject. Contributions of this kind, relating to dies which have been in actual use, are, undoubtedly, of great practical value because they show what has been accomplished and often suggest a method or design that can be used for other classes of work.
In this book various forms of blanking and piercing dies are illustrated and described. All of these designs are, of course, special in the sense that they are intended for producing some particular part, and, at first thought, it might seem useless to study the details of a die which, in all probability, will not exactly be duplicated within the experience of any one toolmaker or die maker. It should be remembered, however, that the best way to obtain a broad, general knowledge of die construction is by studying as many different designs as possible, in order to become familiar with the constructional features which have proved successful in actual practice. Therefore, this treatise deals chiefly with various punch and die designs, and also the methods employed in connection with their construction. Incidentally, some of the tools illustrated represent ingenious types which are the development of long experience in the art of constructing dies.
Tools for Perforating - Cylindrical Work
Very little has been written about the dies used for perforating the sides of cylindrical work. The punches and dies used for this purpose are similar to blanking punches and dies, except for the modifications necessary owing to the fact that the metal which passes over the face of the perforating die is circular in form instead of being flat as with a blanking die. Circular perforating tools are used in connection with this class of work because the nature of the work is such that it cannot, on account of both commercial and mechanical considerations, be carried out in any other way.
Filing Out the Die Shape
A die used for perforating the sides of cylindrical work is rather awkward to hold, either in the vise or in die-clamps while being filed out, owing to the fact that the face of the die is circular in shape and the sides are dovetailed. For this reason, a die-holding fixture, shown in Fig. 20, is used to hold the die in the vise, die-clamp, or filing machine while it is being filed out. The device shown is adjustable to accommodate various widths of dies.
The most essential points to be remembered when filing out a perforating die are: Use a coarse file for the rough filing and finish with a smooth one. Take care to have the clearance filed straight in order to prevent the congestion of scrap punchings in the die; perforating dies as a rule are not very strong and are often cracked and broken because of neglect on this point. The clearance should not be filed over 1 1/2 degree, in order to make the die as strong as possible; in cases where the holes in the dies are close together even less clearance is necessary, and a very narrow wall that separates two holes is filed almost straight on each side, with just enough of a taper to clear. Care must be taken when filing to prevent the back or the sides of the file from running into the finished part of the die.
Making the Punch for a Perforating Die
The punch used with the die shown in Fig. 14 is comparatively simple in its construction. It consists of the usual form of punch holder into which the two perforating punches are driven. The star - shaped punch, after it is fitted to the die and hardened, is driven into the punch-holder in such a position that when it is entered into the die the sides of the punch-holder will be in a straight line and parallel with the die-bed. The tools are then set up in a hand or foot press so that the die and star punch are in proper alignment with each other. The foot treadle of the press is then disconnected from the gate so that the gate which holds the punch-holder in place can be withdrawn from the press without disturbing the punch-holder or the ways upon which the gate slides. The other punch, in its unfinished state, is then driven into the punch-holder and the face is coated with a 1/16-inch thickness of soft solder. The gate of the press is then slipped back into place and the impression of the outline of the die is transferred to the solder on the face of the punch. The punch-holder is then removed from the press and the punch driven out and milled to conform to the soft solder outline of the die, after which the punch-holder is put back into the press, care being taken to see that the star-shaped punch is in proper alignment with the die. The milled punch is then put back in place and gradually sheared and fitted to the die. Each time after the punch has been lightly sheared into the die, the fins and surplus stock are removed and the punch is again entered and sheared a trifle deeper, until it enters the die at least 14 inch. The hand or foot press is very convenient to use when fitting perforating punches to their dies, because the construction of the press makes it possible to handle the gate conveniently and to keep the punches in proper alignment with the die.
SECTIONAL PUNCH AND DIE CONSTRUCTION
A great many dies at the present time are formed of sections instead of being cut out of a solid piece of steel. This sectional construction is employed more particularly for large dies, especially when the form is complicated. The principal reason for making a die in sections, instead of from one solid piece of steel, is that the danger of spoiling the entire die, as the result of warping or cracking in hardening, is eliminated. On the other hand, a solid die is liable to be cracked by the hardening process, and in the case of a large die of complicated form this, of course, means a considerable loss. Some dies are also provided with one or more sections, at points on the die face where the work is severe, so that the die can easily be repaired by simply replacing these sections when they have been worn excessively.
Sectional Die for Piercing- and Blanking 1 Square Washers An example of sectional die construction is shown in Fig. 30. This die is so designed that all the cutting edges and the inside of the die can be machined and ground to the required dimensions without requiring any hand work. This construction makes the punch and die inexpensive to produce, and in event of its being damaged during the hardening process or when placed in operation, the damaged parts can be renewed at a relatively small cost. The punch and die are used in manufacturing laminated copper washers in large numbers. These washers are square and have a square hole in the center; they are produced from sheet copper 0.020 inch in thickness. An inclined power press with automatic roll feed is used, and the finished work slides into a receptacle at the rear of the press.
By referring to the plan and sectional views of the die, it will be seen that there are three piercing and three blanking dies carried on one bolster. The die is made up of fifteen sections which are held together by double dovetail plugs fitting into corresponding holes. When ribbon stock is fed through the die, the holes in three washers are pierced at the first stroke of the ram, and at the next stroke the blanking punch cuts away three washers with the holes in their centers which were produced by the preceding stroke; at the same stroke, the holes are pierced for the next three washers. The diagram, Fig. 31, shows the order of the piercing and blanking operations. None of the sections of the die have been drawn in detail as they will be readily understood from the assembly drawing.
DOWNLOAD FREE BOOK: Modern blanking and piercing dies
In this book various forms of blanking and piercing dies are illustrated and described. All of these designs are, of course, special in the sense that they are intended for producing some particular part, and, at first thought, it might seem useless to study the details of a die which, in all probability, will not exactly be duplicated within the experience of any one toolmaker or die maker. It should be remembered, however, that the best way to obtain a broad, general knowledge of die construction is by studying as many different designs as possible, in order to become familiar with the constructional features which have proved successful in actual practice. Therefore, this treatise deals chiefly with various punch and die designs, and also the methods employed in connection with their construction. Incidentally, some of the tools illustrated represent ingenious types which are the development of long experience in the art of constructing dies.
Tools for Perforating - Cylindrical Work
Very little has been written about the dies used for perforating the sides of cylindrical work. The punches and dies used for this purpose are similar to blanking punches and dies, except for the modifications necessary owing to the fact that the metal which passes over the face of the perforating die is circular in form instead of being flat as with a blanking die. Circular perforating tools are used in connection with this class of work because the nature of the work is such that it cannot, on account of both commercial and mechanical considerations, be carried out in any other way.
Filing Out the Die Shape
A die used for perforating the sides of cylindrical work is rather awkward to hold, either in the vise or in die-clamps while being filed out, owing to the fact that the face of the die is circular in shape and the sides are dovetailed. For this reason, a die-holding fixture, shown in Fig. 20, is used to hold the die in the vise, die-clamp, or filing machine while it is being filed out. The device shown is adjustable to accommodate various widths of dies.
The most essential points to be remembered when filing out a perforating die are: Use a coarse file for the rough filing and finish with a smooth one. Take care to have the clearance filed straight in order to prevent the congestion of scrap punchings in the die; perforating dies as a rule are not very strong and are often cracked and broken because of neglect on this point. The clearance should not be filed over 1 1/2 degree, in order to make the die as strong as possible; in cases where the holes in the dies are close together even less clearance is necessary, and a very narrow wall that separates two holes is filed almost straight on each side, with just enough of a taper to clear. Care must be taken when filing to prevent the back or the sides of the file from running into the finished part of the die.
Making the Punch for a Perforating Die
The punch used with the die shown in Fig. 14 is comparatively simple in its construction. It consists of the usual form of punch holder into which the two perforating punches are driven. The star - shaped punch, after it is fitted to the die and hardened, is driven into the punch-holder in such a position that when it is entered into the die the sides of the punch-holder will be in a straight line and parallel with the die-bed. The tools are then set up in a hand or foot press so that the die and star punch are in proper alignment with each other. The foot treadle of the press is then disconnected from the gate so that the gate which holds the punch-holder in place can be withdrawn from the press without disturbing the punch-holder or the ways upon which the gate slides. The other punch, in its unfinished state, is then driven into the punch-holder and the face is coated with a 1/16-inch thickness of soft solder. The gate of the press is then slipped back into place and the impression of the outline of the die is transferred to the solder on the face of the punch. The punch-holder is then removed from the press and the punch driven out and milled to conform to the soft solder outline of the die, after which the punch-holder is put back into the press, care being taken to see that the star-shaped punch is in proper alignment with the die. The milled punch is then put back in place and gradually sheared and fitted to the die. Each time after the punch has been lightly sheared into the die, the fins and surplus stock are removed and the punch is again entered and sheared a trifle deeper, until it enters the die at least 14 inch. The hand or foot press is very convenient to use when fitting perforating punches to their dies, because the construction of the press makes it possible to handle the gate conveniently and to keep the punches in proper alignment with the die.
SECTIONAL PUNCH AND DIE CONSTRUCTION
A great many dies at the present time are formed of sections instead of being cut out of a solid piece of steel. This sectional construction is employed more particularly for large dies, especially when the form is complicated. The principal reason for making a die in sections, instead of from one solid piece of steel, is that the danger of spoiling the entire die, as the result of warping or cracking in hardening, is eliminated. On the other hand, a solid die is liable to be cracked by the hardening process, and in the case of a large die of complicated form this, of course, means a considerable loss. Some dies are also provided with one or more sections, at points on the die face where the work is severe, so that the die can easily be repaired by simply replacing these sections when they have been worn excessively.
Sectional Die for Piercing- and Blanking 1 Square Washers An example of sectional die construction is shown in Fig. 30. This die is so designed that all the cutting edges and the inside of the die can be machined and ground to the required dimensions without requiring any hand work. This construction makes the punch and die inexpensive to produce, and in event of its being damaged during the hardening process or when placed in operation, the damaged parts can be renewed at a relatively small cost. The punch and die are used in manufacturing laminated copper washers in large numbers. These washers are square and have a square hole in the center; they are produced from sheet copper 0.020 inch in thickness. An inclined power press with automatic roll feed is used, and the finished work slides into a receptacle at the rear of the press.
By referring to the plan and sectional views of the die, it will be seen that there are three piercing and three blanking dies carried on one bolster. The die is made up of fifteen sections which are held together by double dovetail plugs fitting into corresponding holes. When ribbon stock is fed through the die, the holes in three washers are pierced at the first stroke of the ram, and at the next stroke the blanking punch cuts away three washers with the holes in their centers which were produced by the preceding stroke; at the same stroke, the holes are pierced for the next three washers. The diagram, Fig. 31, shows the order of the piercing and blanking operations. None of the sections of the die have been drawn in detail as they will be readily understood from the assembly drawing.
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